spring IOC annotation

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Component {

	/**
	 * The value may indicate a suggestion for a logical component name,
	 * to be turned into a Spring bean in case of an autodetected component.
	 * @return the suggested component name, if any
	 */
	String value() default "";

}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Repository {

	/**
	 * The value may indicate a suggestion for a logical component name,
	 * to be turned into a Spring bean in case of an autodetected component.
	 * @return the suggested component name, if any
	 */
	String value() default "";

}

@Component("userDao")註解在類上，表示定義了一個bean，id爲userDao，和此註解類似的還有：@Repository,@Service,@Controller用來註解dao層，業務邏輯層和控制層，他們都會被解析成bean，只是後面幾個spring會賦予一些特殊功能，所以寫的時候根據類的作用寫不同的註解

要在定義bean的時候，給bean定義scope那麼就再添加一個註解@Scope

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Scope {

	/**
	 * Specifies the scope to use for the annotated component/bean.
	 * @return the specified scope
	 */
	String value() default BeanDefinition.SCOPE_SINGLETON;

	/**
	 * Specifies whether a component should be configured as a scoped proxy
	 * and if so, whether the proxy should be interface-based or subclass-based.
	 * <p>Defaults to {@link ScopedProxyMode#NO}, indicating that no scoped
	 * proxy should be created.
	 * <p>Analogous to {@literal <aop:scoped-proxy/>} support in Spring XML.
	 */
	ScopedProxyMode proxyMode() default ScopedProxyMode.DEFAULT;

}

要實現bean的裝配，那麼使用@Autowired，@Qualifier,@Resource

@Autowired 默認按類型進行裝配，如果找不到就出異常，required屬性定義爲false就不會出異常了

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.CONSTRUCTOR, ElementType.FIELD, ElementType.METHOD})
public @interface Autowired {

	/**
	 * Declares whether the annotated dependency is required.
	 * <p>Defaults to <code>true</code>.
	 */
	boolean required() default true;

}

如果容器中有一個以上的bean匹配，那麼使用@Qualifier限定Bean的名稱，和@Autowired配合使用

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.TYPE, ElementType.ANNOTATION_TYPE})
@Inherited
@Documented
public @interface Qualifier {

	String value() default "";

}

 

@Resource和@Autowired類似,不過@Resource是javax.annotation包下的

@Target({TYPE, FIELD, METHOD})
@Retention(RUNTIME)
public @interface Resource {

@Resource("car") 找id爲car的bean注入，這個註解要求提供一個bean名稱的屬性，如果沒有指定，那麼默認採用標註處的變量名或方法名作爲bean的名稱。與@Resource雷同的還有@Inject，很少使用，建議用@Autowired

@Resource裝配順序
如果同時指定了name和type，則從Spring上下文中找到唯一匹配的bean進行裝配，找不到則拋出異常

如果指定了name，則從上下文中查找名稱（id）匹配的bean進行裝配，找不到則拋出異常

如果指定了type，則從上下文中找到類型匹配的唯一bean進行裝配，找不到或者找到多個，都會拋出異常

如果既沒有指定name，又沒有指定type，則自動按照byName方式進行裝配（見2）；如果沒有匹配，則回退爲一個原始類型（UserDao）進行匹配，如果匹配則自動裝配；

 

在類中定義了這些註解後，要在配置文件中使用context命名空間中的component-scan的base-package屬性指定掃描的路徑,那麼該包以及下面所有的子包中的類都會被掃描

<context:component-scan base-package="com.baobaotao.anno"/>

這個元素裏可以配置掃描哪些類，排除哪些類

<context:component-scan base-package="com.auscend">
		<!-- 安全性配置，如果啓用安全性，請註釋掉 -->
		<context:exclude-filter type="regex" expression="com.auscend.secure.*"/>
		
		<context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
</context:component-scan>		
	

<context:component-scan base-package="com.baobaotao">
       <context:include-filter type="regex" expression="com\.baobaotao\.anno.*Dao"/>
       <context:include-filter type="regex" expression="com\.baobaotao\.anno.*Service"/>
       <context:exclude-filter type="aspectj" expression="com.baobaotao..*Controller+"/>
</context:component-scan>

<context:component-scan base-package="com.baobaotao" resource-pattern="anno/*.class"/>

支持的過濾器類型：

Filter Type	Example Expression	Description
annotation	org.example.SomeAnnotation	An annotation to be present at the type level in target components.
assignable	org.example.SomeClass	A class (or interface) that the target components are assignable to (extend/implement).
aspectj	org.example..*Service+	An AspectJ type expression to be matched by the target components.
regex	org\.example\.Default.*	A regex expression to be matched by the target components class names.
custom	org.example.MyTypeFilter	A custom implementation of the org.springframework.core.type .TypeFilter interface.

練習時請使用ApplicationContext，因爲有些BeanFacory不支持自動依賴注入。